NUMBER OF COUNTRIES 20 |- 10 20 r- AFRICA 0-20 20-40 40-60 60-80 80+ ADJUSTED SCHOOL ENROLLMENT RATIOS3 10 - " n ^ n 1 0-20 20-40 40-60 60-80 80+ ASIAC 20 r ,-, n 20 LATIN AMERICAC 0-20 20-40 40-60 60-80 80+ NORTHERN AMERICA AND EUROPE 0-20 20-40 40-60 60-80 80+ Figure 1. Number of countries in each continent with given levels of adjusted school enrollment ratios, around 1965. aThe adjusted school enrollment ratio is a percentage ratio based on the enrollment in primary and secondary schools (including general, vocational, and teacher training schools) related to the estimated population in the age range to which these levels of education apply in the particular country. bExcludes mainland China. CA11 countries listed by UNESCO under North America, with the exception of the United States, Canada, and Greenland, were included in Latin America. Source: UNESCO (2, Table 2.5). The Quality of Education What has happened to the quality of education while these massive quantitative advances have been taking place? Any answer to this question must be tentative because the quality of a school system is difficult to measure anded in Figure 1—the percentage ratio of enrollments in primary and secondary schools to the estimated school-age population—Pakistan and Nigeria are the least advanced of the world's twenty largest nations.